187037 research outputs found
Sort by
Zero Poisson's ratio metamaterial and meander-inspired diaphragms for enhancing low-frequency performance in flat-panel loudspeaker
No full textFlat-panel loudspeakers, designed with a planar configuration, provide space-efficient audio solutions; however, they frequently exhibit limitations in low-frequency performance due to constrained diaphragm displacement. This study addresses the challenge of enhancing low-frequency sound pressure levels in flat-panel loudspeakers while preserving their slim profiles. We demonstrate that integrating metamaterial-inspired Zero Poisson's Ratio Diaphragms (ZPD) and Edge-Patterned Diaphragms (EPD) significantly improves low-frequency sound pressure levels in piezoelectric flat-panel loudspeakers. The selection of ZPD and EPD designs leverages the unique monoclastic behavior of zero Poisson's ratio structures and the high displacement characteristics of meanderspring patterns, respectively, which results in increased diaphragm flexibility and displacement. Our finite element analysis, supported by experimental results, shows that both ZPD and EPD designs enhance sound pressure levels below 200 Hz compared to a conventional bare diaphragm, achieving maximum enhancements of 11.6 dB and 20.0 dB, respectively. These findings advance the field by introducing diaphragm designs that exploit zero Poisson's ratio principles and structural patterns to improve acoustic performance without increasing overall thickness. The proposed metamaterials and structural designs demonstrate considerable potential for acoustic applications across multimedia systems, portable devices, and automotive audio, where superior low-frequency response in slim-profile loudspeakers is highly beneficial.
A wide-spectrum mid-infrared electro-optic intensity modulator employing a two-point coupled lithium niobate racetrack resonator
No full textOptical intensity modulators (OIMs) are essential for mid-infrared (mid-IR) photonics, enabling applications such as bond-selective molecular sensing, and free-space communications via atmospheric windows. Integrated photonics offers a compact and cost-effective solution, yet on-chip mid-IR OIMs significantly underperform compared to their near-IR counterparts. Furthermore, despite the potential benefits for system reconfiguration in accessing various communication frequencies and molecular absorption bands, developing a single OIM capable of operating across a broad spectral range remains a challenge. In this study, we introduce an on-chip OIM that operates over a wide wavelength range in the mid-IR, implemented using a racetrack resonator structure in thin film lithium niobate (TFLN). The modulator employs a two-point coupling scheme, allowing active control of the coupling strength to maintain critical coupling and thereby ensuring high modulation extinction across a wide spectral region. This approach not only achieves high modulation performance but also relaxes the design constraints and fabrication precision typically associated with resonator-based modulators, as confirmed through an analytic model. Implemented in TFLN having a wide transmission spectrum and strong electro-optic coefficient, the OIM demonstrates a modulation extinction ratio exceeding 20 dB with an electro-optic efficiency of 7.7 V cm over the wavelength range of 3.3-3.8 mu m, which falls within the first atmospheric transmission widow in the mid-IR. This approach can be adapted to other spectral regions, providing a versatile solution for diverse photonic applications. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/).
Ceramic Layer for Multilayer Ceramic Capacitor and Fabrication Method Thereof
No full text본 발명은 다층 세라믹 캐패시터용 세라믹 박막에 관한 것으로, 상세하게, 본 발명에 따른 세라믹 박막은 막형 소결체이며, 상기 소결체는 유전체 및 탄소 성분을 포함하고, 탄소 성분은, 상기 소결체의 라만 스펙트럼 기준 I) 1310 내지 1360 cm-1의 제1영역에 제1피크 존재, II) 1580~1620 cm-1의 제2영역에 제2피크 존재, III) 0.7 ≤ 제2피크의 최대 강도/제1피크의 최대 강도 ≤ 1.2을 만족한다
LANE CHANGE SYSTEM OF AUTONOMOUS VEHICLE
No full text자율주행 자동차의 차선 변경 시스템이 개시된다. 일 실시예에 따른 차선 변경 시스템에 의해 수행되는 차선 변경 방법은, 차량의 주행 상태 정보를 입력받는 단계; 및 차선 변경 알고리즘을 이용하여 상기 입력된 차량의 주행 상태 정보에 대응하는 차선변경 전환 조건을 출력하는 단계를 포함하고, 상기 차량의 주행 상태 정보는, 차량의 주행 정보를 포함하는 차량의 상태 정보와, 차량을 기준으로 주변 차량의 상황인식을 위한 상황 정보를 포함할 수 있다
BOS 유동 가시화 기법의 진동 취약성 보완을 위한 보정 기법 연구
No full textThe Background Oriented Schlieren(BOS) technique can provide a wide and quantitative measurement of the flow density field. However, as the technique is vulnerable to vibration, the technique's accuracy is often affected by environments and test facilities. A vibration tracking marker was introduced to compensate for the vibration error. The background image movement outside the flow region was also tracked to check and correct the vibration of the background image itself. The nozzle flow of a supersonic blowdown wind tunnel was then diagnosed using the improved BOS technique. The result showed that improvement is capable of correcting vibrational errors. However, the technique was still vulnerable to rotational errors. This study complemented the vibration correction method, which is one of the main causes of error in the BOS technique.
MW-rated Induction Motor Control equipped with Fault-Ride-Through Capability for an Electric Propulsion Ship using Model Predictive Control
No full textTherapeutic effects of lomerizine on vasculopathy in Fabry disease
No full textFabry disease (FD) is a lysosomal storage disorder in which alpha-galactosidase (GLA) deficiency leads to a build-up of globo-triaosylceramide (Gb3) in various cell types. Gb3 accumulation leads to the abnormalities of microvascular function associated with FD. Previously, we discovered significant abnormalities in vascular endothelial cells (VECs) derived from FD-induced pluripotent stem cells. We then used a cell-based system to screen a group of clinical compounds for candidates capable of rescuing those abnormalities. Lomerizine was one of the most promising candidates because it alleviated a variety of FD-associated phenotypes both in vitro and in vivo. Lomerizine reduced mitochondria Ca2+ levels, ROS generation, and the maximal respiration of FD-VECs in vitro. This led to a suppression of the endothelial-to-mesenchymal transition (EndMT) and rescued FD-VEC function. Furthermore, FD-model mice (Gla-/-/TSP1Tg) treated orally with lomerizine for 6 months showed clear improvement of several FD phenotypes, including left ventricular hypertrophy, renal fibrosis, anhidrosis, and heat intolerance. Thus, our results suggest lomerizine as a novel candidate for FD therapy.
Dual-Cys bacteriophytochromes: intermediates in cyanobacterial phytochrome evolution?
No full textPrevious studies have identified three families of knotted phytochrome photoreceptors in cyanobacteria. We describe a fourth type: 'hybrid' phytochromes with putative bilin-binding cysteine residues in both their N-terminal 'knot' extensions and cGMP-phosphodiesterase/adenylate cyclase/FhlA (GAF) domains, which we designate as dual-cysteine bacteriophytochromes (DCBs). Recombinant expression of DCBs in Escherichia coli yields photoactive phycocyanobilin (PCB) adducts with red/far-red photocycles similar to those of the GAF-Cys-containing cyanobacterial phytochromes (Cph1s). Incorporation of the PCB precursor, biliverdin IX alpha (BV), gave multiple populations, one of which appears similar to those of cyanobacterial bacteriophytochromes (cBphPs). A crystal structure of FiDCB bound to BV exhibits two thioether linkages between the GAF- and 'PAS-knot'-Cys residues and the C31 and C32 atoms of BV. When expressed in Synechocystis sp. PCC 6803, DCBs incorporate PCB rather than BV. DCBs can be converted to photoactive cBphP-, Cph1-, and tandem-cysteine cyanobacterial phytochrome (TCCP) analogs by removal and/or addition of a cysteine residue by site-directed mutagenesis. This structural plasticity contrasts with our inability to generate functional photosensor analogs by analogous site-directed mutagenesis of TCCP and Cph1 representatives. Phylogenetic analysis demonstrates that DCBs do not form a monophyletic clade and also suggest that Cph1 and TCCP families independently emerged from different lineages of cBphPs, possibly via DCB intermediates.
Ultrafast pulse propagation time-domain dynamics in dispersive one-dimensional photonic waveguides
No full textUltrafast pulses, particularly those with durations under 100 fs, are crucial in achieving unprecedented precision and control in light-matter interactions. However, conventional on-chip photonic platforms are not inherently designed for ultrafast time-domain operations, posing a significant challenge in achieving essential parameters such as high peak power and high temporal resolution. This challenge is particularly pronounced when propagating through integrated waveguides with nonlinear and high-dispersion profiles. In addressing this challenge, we present a design methodology for ultrafast pulse propagation in dispersive integrated waveguides, specifically focused on enhancing the time-domain characteristics of one-dimensional grating waveguides (1DGWs). The proposed methodology aims to determine the optimal structural parameters for achieving maximum peak power, enhanced temporal resolution, and extended pulse storage duration during ultrafast pulse propagation. To validate this approach, we design and fabricate two specialized 1DGWs on a silicon-on-insulator (SOI) platform. A digital finite impulse response (FIR) model, trained with both transmission and phase measurement data, is employed to obtain ultrafast time-domain characteristics, enabling easy extraction of these results. Our approach achieves a 2.8-fold increase in peak power and reduces pulse broadening by 24 %, resulting in a smaller sacrifice in temporal resolution. These results can possibly pave the way for advanced light-matter interactions within dispersive integrated waveguides.
Preliminary Design of NDP-400: Economical Heat Generation for Efficient Desalination
No full textNuclear reactor power for a heat to desalinate the seawater has been deeply considered in Saudi Arabia. For this purpose, the steam temperature shall be required with the relative low temperature around 100.C. The 400MWth nuclear heating reactor (NDP-400) dedicated to supplying heat for desalination is developed with cooperation of Saudi Arabia and South Korea. In order to improve the safety and to achieve the economics goal, the advanced features, in-vessel control rod drive mechanism (IV-CRDM), printed circuit heat intermediate exchanger (PCIHX), and canned motor type reactor coolant pump (RCP) are harmonized with the design of SMART, which is an integral-type SMR developed by KAERI. This paper will describe the main design features and safety analysis results for representative accidents for the NDP-400